Now, there are exercise flash mobs, organized beforehand by type of exercise, time, and location. The workouts include everything from yoga to rollerblading, and are cheap (about $10) or even free. Here's one for IntenSati in New York City's Washington Square Park a few months ago that looks kind of fun--I'll bet the element of surprise gives the workout a different level of energy than you might get in a typical group fitness class, though I have to say I'm not personally drawn to the performance aspect. But hey, you could end up on YouTube, right?

Would you ever participate in a fitness flash mob? Have you ever been in a regular flash mob?